Reversely-connected electric discharge device system



Sept. 28,1948. A F C-AN 2,450,032

N REVERSELY-CONNECTED ELECTRIC DISCHARGE DEVICE SYSTEM Filed Feb. 4,1943 LOAD IZAO

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INVENTOR. ARTHUR F. GA NN BY QJMW HIS ATTORNEY Patented Sept. 28, 1948nnvssssLY-coNNEo'rEn ELECTRIC ms I L cannon DEVICE SYSTEM Arthur F.Cann, Danvers, Mass, assignor to Browning Laboratories, IncWinchester,-Mass.

Application February 4, Serial No. 174,669

- The present invention relates to electric circuits preferablyemploying grid controlled gaseous tubes and is more particularlyconcerned with a circuit in which aloa'd is supplied with alternatingcurrent through a circuit controlled from an independent electricalcontrolled source.

The object of the present invention is to supply to a load circuitalternating current and alternating current power greater than thatwhich may be supplied by one gaseous grid controlled electronic tube. Ii i A further objector the present invention is to employ i two gaseousgrid controlled electronic tubes with the anode of one tube connected tothe cathode ofa second tube and with the cathode of the 'secondtubeconnectedto the anode of the first tube in such-a manner as to obtainthesum ofthe power whichmay be delivered by each of the tubes.

A further object of the'present invention is to fire" the second gaseoustube from thefirst gaseous tube when the first'gaseous tube has beenfired by some o'utsid'e control source as,for instancaasisnal voltage. VI I A further object is to secure alternating current throughaloadcircuit by means of two gaseous grid controlled tubes. Such gaseouscontrolled tubes as areherein described may comprise a cathode, an anodeenclosed in a gaseous vessel with one or more controlled electrodespositioned between the cathode and anode. The so-called Thyratron of theGeneral Electric Company is suitable for this purpose aswell as RadioCorporation of America TypeZOSO tube and 2051 tube. Thesertubesare so'calledhot cathode tu bes in which a heating. current may besupplied-taprovide the. electron emission from the cathode rather-thanrelying upon the-action ofth'e tube to provide the cathode electronemission.

In the operation of tubes of this type, the grid control; electrodecontrols the point of breakdownor passage of" current through the tubewith reference to the potential applied between the cathode and theanode. After the passage of current through such a tube occurs, the gridno longer has control until the current in the tube has been cut off bydecreasing the potential between the cathode and the anode to such a lowpoint that current through the tube will no longer be sustained. Due tothese properties of the tubes it is difficult to operate two such tubestogether particularly if the cathode-anode circuits are parallellyconnected for then the breakdown of one tube will simultaneously reducethe poten- 2 Claims. (01. est-27) 7 tial across the second tube so thatthere will be no power to operate it.

In the present invention two such tubes of the Thyratron or othersimilartype areoperated substantially in parallel in such a manner as toprovide a substantially continuous flow of alternating current from thealternating current source to the loadto be supplied.

Other objects and merits of the present invention will be more clearlyunderstood with reference to the drawingsillustrating the embodiment ofthe invention in which Figure 1 shows a diagram of the circuit of theinvention and Figure 2 shows a curve of currentas applied to the loadcircuit.

As indicatedin Figure 1, there is provided two similar gaseouscontrolled tubes,'T1 and-T2, each of which is provided with cathodes andanodesrespectivelyKnKz and P1, P2. G1 and G: are the control grids ofthetubes T1 and T2 respectively, the secon'dgrid g1 and g2, respectivelybeing connected to the cathode as indicated in Figure l. p it will benoted that the cathode K2 and the anode P1 are connected together bymeans of the lead 10 and that the cathode Ki andthe anode 1 are alsocon'ne'cted'together by means of the lead I I. The alternating currentsupply i2 is applied through load L between the cathode K1 and-the anodePi and sinc'e'the two tubes T1 and T2 are connected in reverse, thesesame leads alsoapply the alternating current'supply voltage between thecathode K2 and the anode P2 of the Thyratron" tube T2. The rest of thecircuit comprises a signal or bias voltage source l3 connected betweenthe cathode K1 and the grid G1 to apply a grid control potential tothegrid G1 forcontrolled operation of the circuit. Thegrid G: of thetube'Tz is connected to the cathode K2 of the same tube througha'shuntc'on-denser-resistance circuit comprising the resistanceR andthecondenser C whilethe terminal of the rid" G1 is alsoconnected'through a neon tube N and the rectifier T3 in series with oneanother to the cathode K1 of the tube T1.

In the operation of the system before any signal bias voltage is appliedto the grid G: of the tube T1, the neon tube N continues to fire throughthe rectifier T3 since this circuit in series with the condenserresistance circuit is always across the A. C. supply line. The condenserC, therefore, becomes charged and maintains a negative bias on thecontrol grid G2 preventing the tube T2 from discharging. When a signalvolta e acts through the control apparatus l3, a negative grid Inthecircuit as shown in Fig ure l,

bias which normally is maintained on G1 of the tube T1 is altered sothat when the positive halfcycle from the alternating current source isapplied to P1 of tube T1 at discharge across the tube T1 is startedwhich in turn reduces the cathodeanode voltage across this tube to a lowvalue which may be approximately 15 volts and is lower than that forsustaining the operation of the neon tube N.

Since the voltage across the condenser C is no longer maintained, itbegins to discharge, during the positive half-cycle applied to the tubeT1, across the resistance R so that the bias onthe grid G: of the tubeT2 gradually reduces from that point onward. The time constant, however,of this circuit is sufficiently long so that 'a negative bias is stillmaintained on the grid G2 when the next positive half-cycle is appliedacross the tube T1. However, if the grid G1 is still not sufilcientlynegative, the tube T1 will again discharge so that the voltage supplysource will not be applied across the condenser C. By the time thissecond positive half-cycle has gone by, the bias on the grid G2 hasdisappeared sufiicie'ntly to permit the discharge of the tube T2 whenthe anode becomes positive with respect to the cathode. This, therefore,permits the flow of current through the lower half of the alternatingcurrent cycle therefore completing the fiow of current through the fullcycle. This will continue as long as the signal voltage is applied andboth tubes will fire, one for the positive half-cycle and the other forthe negative half-cycle.

The circuit including the rectifier Ta and the condenser resistancecircuit is necessary for the operation of the system. When the anode ofT1 is positive, it will be'noted that the rectified current flowsthrough R. During the next half-cycle the anode of T1 is negative and nocurrent fiows through R except that current which has been stored up inthe capacitor C but during this halfcycle the anode of T2 is positiveand thus T2 would fire if the grid did not have a negative'bias whichis'supplied during this half-cycle by the discharge of the capacitor Cthrough R. The rectifier T3 is necessary as otherwise alternatingcurrent would pass through R and the average bias of the tube-T2 wouldbe zero instead of being maintained normally at a negative value.

It is possible to eliminate the neon tube if the value of the resistor Rand the capacitor C are chosen very accurately to provide the properbias values. itself when the voltage drops below the ignition point,which takes place immediately T1 is fired, thus giving a positiveshut-01f of current through By using the neon tube, as high a variationas 20% in values of R and C may be permitted with successful operationof the system.

In thecurve shown in Figure 2, the first hump A is the current flowthrough the tube Tlwhen the negative bias is reduced. During thenegative half of the alternating current cycle, the voltage Theadvantage of the neon tube showson the tube T1 is in the wrong directionto sustain a discharge through this tube while the bias on the tube T2still exists so that no current flows through this half of the cycle.When the next positive half-cycle comes around, however, if the bias onthe tube T1 is still below the firing point, current will again fiow inthis tube, and since in mhe'hgitlve lib-H 01 thrcy'ere the'blai 6n thegrid of the tube T: has reduced sufficiently so that the tube T: willfire as in this half-cycle the positive potential is applied to theanode of the tube and the negative potential to the cathode.

Having now described my invention, I claim:

1. In combination with an alternating current power source ands; load,an electrical control ureuit'ror controlling the power applied to theload comprising two gaseous discharge control tubes reversely connectedbetween the power source through the load, each of said control tubeshaving a cathode and a control grid, signal means connected to one ofsaid control'grids for controlling the dischargeof thetube. a' rectifiercircuit connected between the cathodes o'f-the tubes and *means includedin'said rectifier circuit for applying periodic'allya gradually decayingpotential to the grid of the-other tube forcontrolllng the initiation ofthe discharge across said tube and a neon tube in seriesinsaid rectifiercir cult for opening the circuit when the potential has dropped below agiven desired value.

2. In combination with an alternating current power source'and a load,an electricalcontrol circuit for controlling the power appliedto'theload comprising two" gaseous discharge control tubes reversely connectedbetween the power source through the load -each of said control tubeshaving a cathode and a control grid, signal means connected to one ofsaidcontrol-grids for controlling the discharge of the one tube;arectifier circuit connected between the cathode d the tubes having aparallelly connected resistor and condenser serially-connected insaidrectifier circult and in the circuit of said-second control grid,and a discharge neon tube inscries with said The following reterehoesare or record ill-the file of this patent:

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